The present invention relates to a pattern formation method for forming a resist pattern by irradiating a resist film with exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band, and a pattern formation material to be used in the same.
Currently, in fabrication of a large scale semiconductor integrated circuit, such as a 64 Mbit dynamic random access memory (DRAM), a logic device with a 0.25 xcexcm through 0.18 xcexcm rule and a system LSI including such a memory and a device, a resist pattern is formed by subjecting a chemically amplified resist including a polyhydroxystyrene derivative and an acid generator to pattern exposure using KrF excimer laser (of a wavelength of a 248 nm band).
Moreover, for fabrication of a large scale integrated circuit, such as a 256 Mbit DRAM and a 1 Gbit DRAM with a 0.15 xcexcm through 0.13 xcexcm rule and a system LSI including such a memory, a pattern formation method using, as exposing light, ArF excimer laser operated at a shorter wavelength (of a 193 nm band) than the KrF excimer laser is now under development.
In the chemically amplified resist including a polyhydroxystyrene derivative used in employing the KrF excimer laser, however, an aromatic ring included in the polyhydroxystyrene derivative has such high absorbance against light of a wavelength of a 193 nm band that the exposing light cannot uniformly reach the bottom of a resist film. Therefore, this chemically amplified resist cannot be suitably used when the ArF excimer laser is employed.
Therefore, a chemically amplified resist including a polyacrylic acid derivative having no aromatic ring is being studied as a resist to be used in employing the ArF excimer laser.
In order to form a pattern finer than 0.13 xcexcm, however, it is necessary to use exposing light of a wavelength of a 1 through 180 nm band, namely, a wavelength shorter than that of the ArF excimer laser, such as Xe2 excimer laser (of a wavelength of a 172 nm band), F2 excimer laser (of a wavelength of a 157 nm band), Kr2 excimer laser (of a wavelength of a 146 nm band), ArKr excimer laser (of a wavelength of a 134 nm band), Ar2 excimer laser (of a wavelength of a 126 nm band) or soft-X rays (of a wavelength of a 13 nm, 11 nm or 5 nm band).
Therefore, the present inventors have formed resist patterns by conducting pattern exposure, using exposing light of a wavelength of a 1 through 180 nm band such as F2 excimer laser, on resist films of known resist materials, specifically, a resist material including a polyhydroxystyrene derivative represented by Chemical Formula 1 and a resist material including a polyacrylic acid derivative.
Chemical Formula 1: 
As a result, the resist pattern cannot be formed in a good pattern shape with a rectangular section and much scum (residue) remains on a substrate.
Accordingly, the conventional resist materials, namely, the resist materials used in employing KrF excimer laser or ArF excimer laser, cannot be used in a pattern formation method using exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band.
In consideration of the aforementioned conventional problem, an object of the invention is providing a pattern formation material and a pattern formation method for obtaining a resist pattern in a good shape by using exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band.
In order to achieve the object, the present inventors have variously examined the reason why a resist pattern has a defective sectional shape when formed from a conventional resist material, such as a resist material including a polyhydroxystyrene derivative as a main component, through pattern exposure using exposing light of a wavelength of a 1 through 180 nm band, resulting in finding the following: Since the exposing light of a wavelength of a 1 through 180 nm band has high energy, the polyhydroxystyrene derivative, that is, the main component of the resist material, is directly reacted with the exposing light. Therefore, hydrogen bonded to carbon located at the xcex1-position and constituting the main chain of the resist material is eliminated, so as to cause a crosslinking reaction for bonding polymer radicals from which hydrogen has been eliminated, which degrades the solubility of an exposed portion of the resist film in a developer.
Therefore, the inventors have variously studied on means for preventing the crosslinking reaction of the main chain of the resist material. As a result, it has been found that the crosslinking reaction of the main chain can be prevented by substituting an alkyl group for a hydrogen atom bonded to carbon located at the xcex1-position and constituting the main chain.
Furthermore, when an alkyl group is substituted for the hydrogen atom bonded to carbon located at the xcex1-position and constituting the main chain of the resist film, the main chain decomposes in an exposed portion of the resist film in development of the resist film with an alkaline developer. Moreover, it has been found that since the solubility of the exposed portion of the resist film in an alkaline developer can be thus improved, the dissolution contrast between an exposed portion and an unexposed portion can be improved so as to attain high resolution. The present invention was devised on the basis of these findings.
The first pattern formation material of this invention comprises a base polymer including a unit represented by the following General Formula 1:
General Formula 1: 
wherein R0 is an alkyl group; R1 is a group that is decomposed through irradiation of light; R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the first pattern formation material, an alkyl group is bonded to carbon located at the xcex1-position and constituting the main chain of the base polymer, and the alkyl group is never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, a crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
The second pattern formation material of this invention comprises a base polymer that includes a unit represented by the following General Formula 2 and is decomposed by an acid; and an acid generator for generating an acid through irradiation of light:
General Formula 2: 
wherein R0 is an alkyl group; R2 is a group that is decomposed by an acid; and R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the second pattern formation material, an alkyl group is bonded to carbon located at the xcex1-position and constituting the main chain of the base polymer, and the alkyl group is never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, the crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
The third pattern formation material of this invention comprises a base polymer including a first unit represented by the following General Formula 3 and a second unit represented by the following General Formula 4:
General Formula 3: 
General Formula 4: 
wherein R0 is an alkyl group; R1 is a group that is decomposed through irradiation of light; R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon; at least one of R5 and R7 is an alkyl group and R5 or R7 that is not an alkyl group is hydrogen or a compound including hydrogen and carbon; and R6 and R8 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the third pattern formation material, an alkyl group is bonded to carbon located at the xcex1-position and constituting the main chain of the first unit and to at least one carbon constituting the main chain of the second unit, and the alkyl groups are never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, the crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
The fourth pattern formation material of this invention comprises a base polymer including a first unit represented by the following General Formula 5 and a second unit represented by the following General Formula 6; and an acid generator for generating an acid through irradiation of light:
General Formula 5: 
General Formula 6: 
wherein R0 is an alkyl group; R2 is a group that is decomposed by an acid; R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon; at least one of R5 and R7 is an alkyl group and R5 or R7 that is not an alkyl group is hydrogen or a compound including hydrogen and carbon; and R6 and R8 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the fourth pattern formation material, an alkyl group is bonded to carbon located at the xcex1-position and constituting the main chain of the first unit and to at least one carbon constituting the main chain of the second unit, and the alkyl groups are never eliminated through irradiation of the exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band. Therefore, the crosslinking reaction of the main chain of the base polymer is never caused in an exposed portion of the resist film.
Accordingly, by using any of the first through fourth pattern formation materials, the solubility of an exposed portion of the resist film in an alkaline developer can be improved, so as to improve contrast between an exposed portion and an unexposed portion of the resist film, resulting in increasing resolution of the resist film.
In any of the first through fourth pattern formation materials, the base polymer is preferably an xcex1-methylstyrene derivative.
Thus, the solubility of the base polymer in an alkaline developer can be definitely improved, so as to definitely increase the resolution of the resist film.
The first pattern formation method of this invention comprises the steps of forming a resist film from a pattern formation material including a base polymer having a unit represented by the following General Formula 7; and forming a resist pattern by irradiating the resist film with exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band for pattern exposure and developing the resist film after the pattern exposure:
General Formula 7: 
wherein R0 is an alkyl group; R1 is a group that is decomposed through irradiation of light; and R3and R4are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the first pattern formation method, the aforementioned first pattern formation material is used, so that the solubility of the base polymer in an alkaline developer can be improved in an exposed portion of the resist film.
The second pattern formation method of this invention comprises the steps of forming a resist film from a pattern formation material including a base polymer that has a unit represented by the following General Formula 8 and is decomposed by an acid, and an acid generator for generating an acid through irradiation of light; and forming a resist pattern by irradiating the resist film with exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band for pattern exposure and developing the resist film after the pattern exposure:
General Formula 8: 
R0 is an alkyl group; R2 is a group that is decomposed by an acid; and R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the second pattern formation method, the aforementioned second pattern formation material is used, so that the solubility of the base polymer in an alkaline developer can be improved in an exposed portion of the resist film.
The third pattern formation method of this invention comprises the steps of forming a resist film from a pattern formation material including a base polymer having a first unit represented by the following General Formula 9 and a second unit represented by the following General Formula 10 and forming a resist pattern by irradiating the resist film with exposing light of a wavelength of a 1 through 30 nm band or a 110 through 180 nm band for pattern exposure and developing the resist film after the pattern exposure:
General Formula 9: 
General Formula 10: 
wherein R0 is an alkyl group; R1 is a group that is decomposed through irradiation of light; R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon; at least one of R5 and R7 is an alkyl group and R5 or R7 that is not an alkyl group is hydrogen or a compound including hydrogen and carbon; and R6 and R8 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the third pattern formation method, the aforementioned third pattern formation material is used, so that the solubility of the base polymer in an alkaline developer can be improved in an exposed portion of the resist film.
The fourth pattern formation method of this invention comprises the steps of forming a resist film from a pattern formation material including a base polymer having a first unit represented by the following General Formula 11 and a second unit represented by the following General Formula 12, and an acid generator for generating an acid through irradiation of light; and forming a resist pattern by irradiating the resist film with exposing light of a wavelength of a 1 through 30 nm band and a 110 through 180 nm band for pattern exposure and developing the resist film after the pattern exposure:
General Formula 11: 
General Formula 12: 
wherein R0 is an alkyl group; R2 is a group that is decomposed by an acid; R3 and R4 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon; at least one of R5 and R7 is an alkyl group and R5 or R7 that is not an alkyl group is hydrogen or a compound including hydrogen and carbon; and R6 and R8 are the same or different and selected from the group consisting of hydrogen and compounds including hydrogen and carbon.
In the fourth pattern formation method, the aforementioned fourth pattern formation material is used, so that the solubility of the base polymer in an alkaline developer can be improved in an exposed portion of the resist film.
Accordingly, in any of the first through fourth pattern formation methods, the solubility of the resist film in an alkaline developer can be improved in an exposed portion of the resist film, so as to improve the contrast between an exposed portion and an unexposed portion of the resist film, resulting in increasing the resolution of the resist film.
In any of the first through fourth pattern formation methods, the base polymer is preferably an xcex1-methylstyrene derivative.
Thus, the solubility of the base polymer in an alkaline developer can be definitely improved in an exposed portion of the resist film, so as to definitely increase the resolution of the resist film.
In any of the first through fourth pattern formation methods, the exposing light is preferably F2 excimer laser, Ar2 excimer laser or soft X-rays